if there is not any built in reader for epub files for WinCE,
Then how I can do it?

Calibre (has its own forum here) can convert between a wide range of ebook formats. If your ePubs have DRM (encryption) you will have to first remove the DRM. Once you have a DRM-free ePub, Calibre can convert it to an ebook format you have a reader for.

If you purchased the ePub files using the Adobe Digital Editions program, they are probably encrypted. In order to remove the DRM to read them with another program, you'll need to find the Adobe Inept script to use with Python program. (It's a complicated process, and the forum rules require that we not go into detail about it.)

However, if you can read the ePub files on a program like Stanza, or with Calibre (which are both free downloads that work for Windows, but don't run on WinCE), then you can use a program to convert the ePub into a .lit file.

I believe Mobipocket software and Calibre will both convert to .mobi format, which can be read on WinCE with Mobipocket's reader. (You could also convert to Palm EReader, but there's no reason to do so.)

I have checked by converting ePub files to others formats like HTML, txt, lit, pdf, pdb by ABC Amber ePub Converter. Then opened this file in WinCE device.

But the problem is this I want to open ePub files directly in WinCE device. Because if user put ePub files in Storage Card of WinCE device and he want to see it, he must not need to convert first to other formats than he will be able to see it in the device.
kindly understand the exact problem and suggest me well!
???

I have checked by converting ePub files to others formats like HTML, txt, lit, pdf, pdb by ABC Amber ePub Converter. Then opened this file in WinCE device.

But the problem is this I want to open ePub files directly in WinCE device. Because if user put ePub files in Storage Card of WinCE device and he want to see it, he must not need to convert first to other formats than he will be able to see it in the device.
kindly understand the exact problem and suggest me well!
???

naveed, Let me try to explain this in a simple manner:

1) There is no way to read DRM'd EPUBs directly in windows CE. You will have to strip the DRM first and then load it on the WinCE device.

2) If the Epub files are not DRM'd then you can use Zulureader software: http://www.zuluexpress.com/ZuluMobile.aspx
Install that and you should be able to read EPUB files (non DRM'd) without needing to do any conversions.

ZuluReader will run on CE devices, there is a CAB download for CE on the site www.zuluexpress.com. Zulureader will only read DRM free epubs though. What device do you have? ZR was developed for small display devices, 640x480 or less but I have people testing it on large screen (1024x768) CE devices and I am working with them to make ZR suitable for all screen sizes. If you have any problems installing or using ZR you can email me at stevedales@gmail.com.